In the formation of spools of yarn upon a core sleeve, the latter may be mounted upon a spindle on a spindle rail accommodating a multiplicity of spindles in a twisting frame in which each spindle is surrounded by a ring along which a traveller orbits the spool as it is formed.
The yarn or thread to be wound up in the spool, usually coming from a drafting frame or the like, forms a balloon around the sleeve of spindle and passes through the traveller before reaching the spool that is formed on that sleeve.
In German patent document DE 41 15 186 C2, a process has been described for varying the speed of the spindles of such a twisting machine and, in that case, the speed of the spindles can be varied with respect to a basic speed during each lifting movement of the ring rail, i.e. the rail carrying the rings upon which the travellers orbit the respective spindles. In this case, moreover, the speed can be reduced with increasing distance between the supply unit and the traveller and ring arrangement, or increased with decreasing distance between the supply unit and the traveller/ring arrangement.
The supply unit can be a drafting frame or other source of the threads or yarns which are to be twisted together. The spindle speed thus varies as a function of the yarn balloon height which is a function of the ring rail position, usually to maintain the yarn tension in the yarn balloon at an approximately constant value during the entire twisting and spool formation operation.
In practice it is found that to maintain an approximately uniform thread tension in the yarn balloon, in the formation of a so-called flyer winding, where the winding layers are substantially parallel to one another, or a so-called composite winding in which, over the major part of the spool, the layers are parallel but at the ends of the spool, conical winding layers are provided, the spindle speed must be repeatedly raised and lowered as a ring rail rises and falls. This has been found to require a large energy consumption for the acceleration and deceleration of the spindles and to significantly stress the spindle drive with drawbacks with respect to maintenance and the like.